All the interviews I've heard with "former smash 'n grab burglar now turned security consultant" types convey the same message: "If I couldn't get in-and-out of the house in 5-7 minutes, I didn't bother. After that time, the chances of the cops showing up get too high to stay in the house. The goodies were almost always in the bedroom closet or drawers."
Watching these guys doing an on-the-fly casing of the house and grabbing goodies would make a time/motion efficiency expert drool. They move very fast, very smooth, and very efficiently. It's mighty educational, as well as entertaining, to see these guys stage a "break-in" on someone's house as part of the tv program to show both how easy it is and the consistency of human behavior in stashing goodies.
The safe doesn't make it impossible to lose your goodies. It makes it inconvenient enough for the bad guys to get your goodies that they'll move down the block to easier pickings. The safe's job is to make your valuables heavy/awkward enough to carry out that the burglars won't take the time to open it or haul it out.
The things that these former bad guys say are deterrents to burglars are obvious alert neighbors (#1 on their "I hate to see it" list), loud dogs, alarms & lights, and indications of security monitoring of the house (signs on the yard, stickers in the windows, etc).